Phosphonitrile elastomers

ABSTRACT

COPOLYMERS WERE PREPARED WHICH CONTAINED THE RANDOM REPEAT UNITS   -(P(-Q)(-Q&#39;&#39;)=N)X-   IN WHICH Q IS EITHER F(CF2)PCH2O- OR H(CF2)PCH2OAND B IS EITHER RC8H4O OR RZC6H4O. THE VALUE OF P IS NOT GREATER THAN 9; Z IS -CH2-, OXYGEN, NH OR NR&#39;&#39; AND R AND R&#39;&#39; ARE H(CH2)Q-, OR F(CF2)Q- WHERE Q IS 0 TO 5. THESE COPOLYMERS WERE FOUND TO BE MUCH MORE STABLE THAN THE POLY(PHOSPHAZENES) REPORTED IN THE PAST.

United States Patent 3,700,629 PHOSPHONITRILE ELASTOMERS Kennard A. Reynard, Mentor, and Selwyn H. Rose, Beachwood, Ohio, assignors to Horizons Incorporated, a division of Horizons Research Incorporated No Drawing. Filed Mar. 26, 1971, Ser. No. 128,496 Int. Cl. C08g 33/16 US. Cl. 26047 P Claims ABSTRACT OF THE DISCLOSURE Copolymers were prepared which contained the random repeat units in which Q is either F(CF CH O or H(CF ),,CH O' and B is either RC H O or RZC H O. The value of p is not greater than 9; Z is -CH oxygen, NH or NR and R and R are H(CH or F(CF where q is 0 to 5. These copolymers were found to be much more stable than the poly(phosphazenes) reported in the past.

This invention relates to copolymers of increased thermal stability which contain repeating units in the polymer chain.

The preparation of related copolymers and terpolymers is described in US. Pat. No. 3,515,688 issued June 2, 1970, and in a copending United States application Ser. No. 33,871 filed May 1, 1970. The poly(phosphazenes) therein described are high molecular weight, elastomeric, chemically resistant copolymers or terpolymers with relatively low glass transition temperatures. The disclosures of these specifications are incorporated herein by reference. The copolymers and terpolymers disclosed in these specifications are thermally stable to temperatures up to about 300 C. on a thermobalance.

Homopolymers of poly(phosphazenes) have been described, for example, in Inorg. Chem. 5, 1709 (1966) and in US. Pat. No. 3,370,020 issued Feb. 20, 1968. These homopolymers are dissolved by common organic solvents, attacked by mild chemical reagents such as dilute acids and depolymerize at or below 150 C. These known homopolymers a z 2 n- We have found that when copolymers containing randomly repeating units [ts-l in the polymer are prepared, the copolymers have unexpectedly superior high temperature stability provided Q and Q are suitably selected. As in US. Pat. No. 3,515,- 688, substituent Q is either F(CF CH 0' or H CF CH O- Substituent Q is either RC H O or RZC H O- in stead of being a fiuoroalkoxy radical diiferent from Q as in U.S. Pat. No. 3,515,688. The 'value of p is not greater than 9, Z is oxygen, CH NH or NR and R and R are H(CH or F(CF where q is 0 to 5.

3,700,629 Patented Oct. 24, 1972 These polymers contain the randomly distributed units of the type and the ratio of QzQ' is between 1:9 and 3:1. These copolymers are elastomers or plastics and are stable to over 400 C. when measured on a thermobalance. This improved thermal stability makes these materials highly useful as seals, gaskets, adhesives, coatings and the like at temperatures Where other phosphazene polymers are not stable.

Some beneficial effects are obtained with as little as ten percent of Q type sidechains with the effects decreasing above 50 percent.

While we do not wish to be bound by any specific theoretical explanation, it appears that the improved stability results from the following factors. Substituents of type Q are more electron withdrawing than substituents of type Q. This electron withdrawing elfect tends to stabilize the PN backbone and depolymerization is retarded. However, substituents of type Q are also quite bulky resulting in considerable steric strain which causes the polymers to depolymerize at lower temperatures. The presence of small amounts of substituents of type Q tend to relieve this steric strain with retention of the stabilization effect of type Q substituents. This relief of steric strain coupled with the high electron withdrawing effect results in copolymers considerably more thermally stable than either homopolymer, and more thermally stable than fluoroalkoxy copolymers of the type described in US. Pat. No. 3,515,688.

The copolymers of the present invention are prepared by reacting a mixture of at least two dilferent alkali metal salts, namely an alkali metal salt of a fluoroalkoxide and an alkali metal salt of an aryloxide with linear soluble [PNC121 polymer. For example, a benzene solution of the linear soluble [PNCI polymer was added to an excess equimolar mixture of the sodium salts of the alcohols of Q and Q in tetrahydrofuran and reacted under suitable conditions. A copolymer corresponding to resulted. These copolymers are colorless, linear, high molecular weight materials and are completely substituted. They usually have low glass transition points and are usually thermally stable to over 400 C. as measured on a thermobalance.

The solubilities of these copolymers vary widely with the nature of the Q and Q groups. Some materials are soluble in most common organic solvents while other copolymers are soluble only in certain fluorocarbon solvents.

The invention is illustrated by the following examples, which are not intended to limit the invention.

EXAMPLE 1 (a) Preparation of poly(dichlorophosphazene) The trimer or tetramer or other low polymer of dichlorophosphazene was prepared from PCl and NH CI by conventional techniques. The [PNCl was recrystallized from hexane with activated charcoal to remove trace impurities. M.P. 112-115 C.

Hexachlorophosphazene was polymerized by conventional techniques under 'vacuum at 250:0.5" until an appropriate melt viscosity was reached. After the sample cooled, the polymerization tube was broken under a nitrogen atmosphere and the bulk of the polymer added to a flask containing 500 ml. of dry benzene protected by a nitrogen atmosphere. It normally took about 24 hours for all of the linear poly(dichlorophosphazene) to dissolve. The polymer was stored in the absence of moisture and was used promptly since after standing several days the material cross-links to form an insoluble gel.

4 obtained with similar solubilities to the copolymer prepared in Example 1.

Analysis.-Calculated for (b) ig g fig fi gggfgfgiggigfigg with substituent ratio of 3:1. (percent): C, 30.0; H, 2.3; N, 5.8; F, 35.7. Found (percent): C,-29.3; H, 2.4; N, The sodium phenoxide (0.52 mole) and sodium tri- 5.9; F, 37.5; Cl, 0.1. This copolymer had an intrinsic fiuoroethoxide (0.52 mole) were prepared in 300 ml. of viscosity of 1.25 dl./g. in acetone and exhibited an initial dry diglyme by the addition of the alcohols to sodium decomposition point of 375 C. when measured on a (0.95 mole). When reaction was complete the solution thermobalance. was heated to 125 C.1 and 50 g. of the [PNCl poly- EXAMPLE 4 mer mixture dissolve in about 275 ml. benzene was added dropwise. The reaction temperature slowly fell Sodlum z i i 88 cllleptafiuofiogut?xlde to 101 C. Reflux was continued for several hours after E fi s Z 1 s. y m addition was complete. Then the mixture was cooled and roxln t 3 g o s 1 e eac an S0 mm hydrolyzed with dilute acid. The organic layer was treated m9 6) 0 22 solutlondof g [Piqclflx polymer with 3 liters isopropanol and the white polymeric preg imole.) i g ded f the alkox cipitate was isolated and dried. The polymer was dises 3 16 W g g at i Re ux g g solved in benzene, washed with water and precipitated 20 g: Y i t e.soupy mhxture was coo e fter by addition to petroleum ether The polymfir was redis y o ysis wit dilute acid, the mixture was concentrated solved in benzene, washed again with water and preby eva'poianon and f i q w1t.h water The coliolymer cipitated by addition of petroleum etherwas obtained by precipitation lnto benzene. Twice, the Analysis calculated for copolymer was dISSOlVC d 1n the azeotrope of acetone and CCl FCClF and precipitated into benzene. The copoly- [NP (OCH CF -NP(OC H 21 mer had an intrinsic viscosity of 2.2 dl./ g. in the azeotrope copolymer with substituent ratio of 1:5 (percent): C, glven 54.9; H, 3.8; N, 6.0; F, 8.2. Found (percent): 0, 55.2; Ample-Calculated for H, 4.1; N, 6.2; F, 9.2; Cl, 0.52 This fibrous plastic had [NP(OCH C F-;) NP(OC H an intrinsic viscosity 0 3.51 dl. g. in benzene and showed an initial decomposition point by thermogravimetric Sub stltuent ram) of Z analysis (TGA) of C. 3.7, F, 49.2. Found (percent). C, 28.0, .H, 1.8, N, 3.8; F, 48.7; Cl, 0.04. The leathery elastomer had an XA 2 initial decomposition point of 400 C. when measured Sodium phenoxide was prepared in 50 ml. of dry tetraon a thermobalance EXAMPLE 5 hydrofuran from phenol (0.062 mole) and sodium (0.059 mole). Sodium trifiuoroethoxide was prepared Sodium phenoxide and 2 CF H were "prefrom trifiuoroethanol (0.059 mole) and sodium (0.057 pared and reacted in similar fashion and amounts as mole). The sodium trifiuoroethoxide solution was added given in EXample After hydrolysis and Concentration dropwise to a cooled (0-5" C.) benzene l ti n f 40 of the reaction mixture, the copolymer was isolated by purified poly(dichlorophosphazene) (0,056 mole), Th precipitation into benzene. The dried material was dissodium phenoxide solution was then added dropwise, solved in acetone twice and precipitated once into ben- The solution was refluxed overnight, cooled and hydrozene and once into water. The white elastomer had an lyzed with dilute hydrochloric acid. After the reaction intri sic Vi C itY f 2.16 dL/g. in acetone. mixture was concentrated by evaporation, the polymer Analysis--Calculated for 25.322233115355112? [NP CHZ CF2 smeNPwcsHmh with a substituent ratio of 7:3 (percent): C, 28.6; H, [NP(OOHZCFS)ZNP(OCGH5)Z]n 1.3; N, 2.5; F, 56.8. Found (percent): 0, 28.2; H, 1.3; with a substituent ratio of 1:1 (percent): C, 40.5; H, 3.0; N, 2.4; F, 55.5; Cl, 0.05. The initial decomposition point N, 5.9; F, 24.1. Found (percent): C, 39.8; H, 2.9; N, as measured on a thermobalance was 390 C.

EXAMPLES 6-11 Example Q Q Q:Q

C;H5O 3:7 Plastic 'IGA 450 c. H(CF2)5CH2O- (3111;0- 3;? Elastomer TGA 425 0. H(OF)CH2O CH3OCQH40 2:1 Elastomer TGA 375 0. (CFzhCHzO- (oH;)2No;H40 1:1 Elastomer TGA 400 C.

CF2)3CH20 CF3C6H40'" 1:4 Plastic TGA 465 0. 11 H(0Fz).0H;0- C2H5ClH40- 1:1 Elastomer TGA 400 0.

6.1; F, 22.9; C1, 0.3. The copolymer is a white elastomer We claim:

which is soluble in benzene and acetone and had an intrinsic viscosity of 3.26 dl./ g. in acetone. The polymer had an initial decomposition point on the thermobalance of about 425 C. in nitrogen.

EXAMPLE 3 Sodium (2.12 moles), trifiuoroethanol (1.16 moles) 1. A poly(-phosphazene) copolymer consisting essentially of randomly distributed units of the formula and Phenol moles) Were Placed in 150 y wherein Q represents a monovalent radical selected from tetrahydrofuran and refluxed until sodium was no longer visible. A benzene solution of purified [PNCI (0.65 mole) was added dropwise to the alkoxide mixture at reflux. The reaction mixture was refluxed, hydrolyzed the group consisting of F(CF CH O-- and H(CF CH O- and p is an integer from 1 to 9 and wherein Q repand purified as in Example 1. A colorless elastomer was resents a monovalent radical selected from the group consisting of RC H O and 1 2ZC H O-- wherein R is 8. A copolymer of claim 1 whereinQ is selected from the group consisting of H(CH and F(CFZ)3CHZO News and Q is CF C H O--. in which q is 0 to 5 and Z represents a divalent mem- 5 9. A copolymer of claim 1 wherein Q is ber of the group consisting of CH O, NH, and NR' wherein R' is a monovalent radical selected H(CF2) 6CH2O from the group consisting of H(CH and F(CF and Q '18 C H C H O. I in which q is 0 to 5, and the ratio of A:B is between 10. A copolymer of claim 1 wherein the ratlo of QzQ' 1:9 and 3:1. 10 is between 1:4 and 2:1.

2. A copolymer of claim 1 wherein Q is C H O. 3. A copolymer of claim 2 wherein Q is CF CH O-. References Cited 4. A copolymer of claim 2 wherein Q is UNITED STATES PATENTS H(CF CH O 15 3,370,020 2/1968 Allcock et a1. 260-2 5. A copolymer of claim 2 wherein Q is 3,515,688 6/1970 Rose H(CF CH O '6. A copolymer of claim 1 wherein Q is WILLIAM Pnfnary Exammer H(CF2) 6CH2O L. L. LEE, Asslstant Examiner and Q is CH OCgH O. US. 01. X.R.

7. A copolymer of claim 1 wherein Q 15 260 328 N 33.6 F, 333 F F(CF CH O and Q is (CH NC I-I O. 5 

